The spark ignition gasoline engine is generally used for small vehicles, and in the foreseeable future, such use will continue to prevail. Since the crisis of energy shortage is going to increase with each passing day, how to save fuel is naturally of very great importance in our daily life. Therefore, to modify the existing spark ignition gasoline engine to increase its efficiency and so that it can use more than one type of fuel for the purpose of saving energy has become more and more significant to the world than ever before.
In using multi-fuels, such as kerosene, diesel fuel, mixed oil or alcohol in gasoline engines, the first problem encountered is that the amount of air to be mixed for each kind of fuel is different as a result of the difference in individual molecular weight; and the second problem is that the conditions required for overcoming the knock combustion problems of individual kinds of fuel are not the same. These two problems can be solved by the concept of this invention saving fuel.